This invention relates to the structure of a needle-type lens for observing a living body.
A conventional needle-type lens for observing the interior of a living body is constructed as shown in FIGS. 4 to 6. In these Figures, a relay lens 2 of a bar-like shape is inserted in an inner tube 1, and a support member 3 of a generally cylindrical shape is mounted on one end of the inner tube 1. An ocular lens 4 is mounted within the support member 3, and is disposed on the optical axis of the relay lens 2. A solid charge-coupled device (CCD) (not shown) is connected to the end of the support member 3 remote from the end thereof on which the inner tube 1 is mounted. A funnel-shaped condenser guide 5 made of an acrylic resin is mounted on the outer periphery of the inner tube 1 in intimate contact therewith. The proximal end portion of this condenser guide is increasing in diameter, and fits on the outer periphery of the support member 3, and is fixed thereto by a plurality of fixing screws 6.
In the needle-type lens 7 of the above construction, its distal end is inserted into a portion of a living body to be observed, and light emitted from a light source (not shown) is applied via the condenser guide 5 to the portion to be observed, and an image of the observed portion is projected onto the CCD in a magnified manner through the relay lens 2 and the ocular lens 4. The image projected on the CCD is converted into an electrical signal, and is displayed on a display device via a processing circuit.
In the conventional needle-type lens structure of the above construction it is difficult to manufacture the condenser guide 5, because an acrylic resin must be formed into an elongated tubular shape. Furthermore, the surface of this condenser guide can be easily damaged resulting in light leading through the damaged portion. The condenser guide has further drawbacks in that it may be deformed upon the lapse of time and, it can be corroded by chemicals. As a result, there is a risk that the portion to be observed will not be illuminated sufficiently.
As described above, in the conventional needle-type lens structure, it, is difficult to manufacture the condenser guide, which is formed into an elongated tubular shape, using an acrylic resin. Furthermore, the condenser guide can be damaged at its surface, and is corroded by chemicals and/or deformed. As a result, sufficient illumination can not always be provided.